Wagner, Verdi and Britten.

Richard, Giuseppe and Ben. The German ideologue, the ardent Italian and the English pacifist. They're an unlikely trio, these birthday boys, but the classical music world loves nothing more than an anniversary (or three) around which to plan its programmes, so for the course of 2013 these disparate titans get to share the celebratory spotlight. Wagner (1813-1883) and Verdi (1813-1901) were the same age exactly but never met or showed much open respect for each other. Britten (1913-1976) was a century younger and cultural worlds apart.

Still, there are reasons beyond coinciding birthdays to talk about Wagner, Verdi and Britten in the same breath. Take the issue of nationhood. All three composers were held up during their lifetimes, and for posterity, as respective national treasures. All three were granted pride of place in their national musical lineage. All three had complicated relationships with their homelands.

Britten was born, died and lived most of his life in Suffolk. His music is soaked in the county's landscapes, fishing villages, people and especially its sea. He was a local lad through and through, but his broader sense of Englishness was heartfelt too: "I'm English," he said when he was living in New York in the early 1940s, "and as a composer I suppose I feel I want more definite roots than other people."

He believed in roots, "in associations, in backgrounds". But England wasn't always easy for him. He was gay, which was illegal until 1967, and he was a pacifist, which posed its challenges during and after the Second World War. Yet he became a national treasure almost as soon as Peter Grimes premiered in 1945. Despite his leftism, his pacifism and his homosexuality, he was tasked to write the opening music for Basil Spence's new Coventry Cathedral in 1962 – a hugely patriotic gig. Britten accepted his cultural status but kept his War Requiem on his own terms, deeply anti-militaristic. He was a complicated Englishman.

Verdi was more of a chancer, blessed with right-place, right-time luck. In the 1860s and 1870s the fledgling Italian nation was scrambling for cultural icons on which to build up its new identity. Verdi's early work was hardly responsible for the revolutions that led to the country's founding in 1861, but he became the de facto poster boy of the Risorgimento (literally The Resurgence – Italian unification) and happily jumped on the bandwagon. In the late 1850s the slogan Viva VERDI caught on: it stood for Viva Vittorio Emanuele Re D'Italia, linking the composer's popularity with the future first King of Italy.

Verdi remained a handy political mascot from beyond the grave. In 1941, in the midst of the Second World War, Benito Mussolini made sure Italy celebrated the 40th anniversary of the composer's death in style, publishing a commemorative pamphlet with a picture of himself enjoying Verdi's music. The association didn't seem to do much lasting damage; Verdi remains Italy's best-known and best-loved opera composer – so much so that when Milan's opera house La Scala scheduled Wagner, not Verdi, to open this year's season of centenary celebrations, it caused little short of a national uprising.

And Wagner? Being Hitler's favourite composer didn't do his reputation many favours, but a lot of his bad press was self-inflicted. A lot of it was self-penned: Wagner spared no efforts in jotting down his rampant anti-semitism, for example. And when it comes to his national myth-making, look no further than the final scene of Die Meistersinger von Nurnberg, in which the wholesome cobbler Hans Sachs sings of the virtues of pure German art and the dangers of foreign infiltration. Wagner died long before the Nazis came to power, but the sentiments are there in his own hand, sealed on the page for grim posterity.

Whether or not that influences how you listen to Wagner's music is a personal choice. There can be no denying the impact he had in artistic terms. Between them, he and Verdi rewrote the operatic rulebook, upturned its conventions, sent its subject matters soaring to eternal ecstatic love (Tristan und Isolde) and crashing down to sordid real life (La Traviata). Wagner was, in broader musical terms, the greater innovator. His adventures in non- functional harmony set the stage for Schoenberg's atonalism, for Debussy's impressionism and for pretty much everything that followed. It is clichéd but it is true: all of Western music changed with those four loaded notes of the Tristan chord.

Verdi took bold strides of his own. He ditched the rampant floridity of Bellini, Donizetti and Rossini to create an operatic language that was, above all, direct. He scrubbed away at formalised structures, took a broad overview of dramatic thrust, chose words and musical styles he knew his audience could relate to and be moved by. Verdi's sopranos really belted, using their chest voices to project rather than their head voices to decorate – think of them as the original soul singers.

In honing his language Verdi was able to treat subject matters that were out of everyday life not out of legend: La Traviata's Violetta is a prostitute who dies of consumption, a disease many in the original audience would have come into contact with. True verismo (operatic "realism") came later, but Verdi made giant steps in that direction.

Across the English Channel, 100 years later, Britten wrote operas of seething, uncomfortable home truths.

He used modernist 12-tone techniques, but generally kept his soundworld rooted in tonality; his main business – at least when it came to his operas – was exploring the deeper themes that preoccupied him until death. Relationships between men; the corruption of innocence; the lone dreamer driven to ruin by the crowd – Britten's favourite themes were deeply personal and deeply felt.

He had a fabulous way of handling words. He was able to set texts from Shakespeare to Wilfred Owen, WB Yates to Henry James in ways that twisted and played with and elevated the words. The Turn Of The Screw, a James ghost story, is the most deeply creepy of his 16 operas; Death In Venice is the most personally candid; A Midsummer Night's Dream is the most darkly fantastical. But Peter Grimes, his first full-length opera, remains the masterpiece. Premiered at Saddler's Wells in 1945 and marking Britten's international breakthrough, the story of the Aldeburgh fisherman speaks as powerfully today as it did to its first audiences.

Scottish Opera doffs its cap to all three composers this spring. A Midsummer Night's Dream is the annual co-production between SO and the Royal Conservatoire of Scotland that opens later this month. Annilese Miskimmon's excellent touring production of Verdi's La Traviata continues to trundle around the Highlands – catch it if you can – and The Flying Dutchman, Wagner's ghostly seafaring epic, hits the Theatre Royal stage at the beginning of April.

Meanwhile, happy birthday, boys. Somehow I hope you're together blowing out birthday candles in the sky.